Transmural ablation device with integral EKG sensor

ABSTRACT

A method and apparatus for transmural ablation using an instrument containing two electrodes or cryogenic probes. A clamping force is exerted on the two electrodes or probes such that the tissue of the hollow organ is clamped therebetween. Bipolar RF energy is then applied between the two electrodes, or the probes are cryogenically cooled, thus ablating the tissue therebetween. A monitoring device measures a suitable parameter, such as impedance or temperature, and indicates when the tissue between the electrodes has been fully ablated.

CROSS REFERENCE TO RELATED APPLICATION

[0001] This application is a continuation-in-part of application Ser.No. 09/844,225 filed Apr. 27, 2001, which is a continuation in part ofapplication Ser. No. 09/747,609 Dec. 22, 2000, which claims the benefitof provisional application Serial No. 60/200,072, filed Apr. 27, 2000.

BACKGROUND OF THE INVENTION

[0002] Atrial fibrillation is the most common heart arrhythmia in theworld, affecting over 2.5 million people in the United States alone.Ablation of cardiac tissue, in order to create scar tissue that poses aninterruption in the path of the errant electrical impulses in the hearttissue, is a commonly performed procedure to treat cardiac arrhythmias.Such ablation may range from the ablation of a small area of hearttissue to a series of ablations forming a strategic placement ofincisions in both atria to stop the conduction and formation of errantimpulses.

[0003] Ablation has been achieved or suggested using a variety oftechniques, such as freezing via cryogenic probe, heating via RF energy,surgical cutting and other techniques. As used here, “ablation” meansthe removal or destruction of the function of a body part, such ascardiac tissue, regardless of the apparatus or process used to carry outthe ablation. Also, as used herein, “transmural” means through the wallor thickness, such as through the wall or thickness of a hollow organ orvessel.

[0004] Ablation of cardiac tissue may be carried out in an open surgicalprocedure, where the breastbone is divided and the surgeon has directaccess to the heart, or through a minimally invasive route, such asbetween the ribs or via catheter that is introduced through a vein, andinto the heart.

[0005] Prior to any ablation, the heart typically is electronicallymapped to locate the point or points of tissue which are causing thearrhythmia. With minimally invasive procedures such as via a catheter,the catheter is directed to the aberrant tissue, and an electrode orcryogenic probe is placed in contact with the endocardial tissue. RFenergy is delivered from the electrode to the tissue to heat and ablatethe tissue (or the tissue may be frozen by the cryogenic probe), thuseliminating the source of the arrhythmia.

[0006] Common problems encountered in this procedure are difficulty inprecisely locating the aberrant tissue, and complications related to theablation of the tissue. Locating the area of tissue causing thearrhythmia often involves several hours of electrically “mapping” theinner surface of the heart using a variety of mapping catheters, andonce the aberrant tissue is located, it is often difficult to positionthe catheter and the associated electrode or probe so that it is incontact with the desired tissue.

[0007] The application of either RF energy or ultra-low temperaturefreezing to the inside of the heart chamber also carries several risksand difficulties. It is very difficult to determine how much of thecatheter electrode or cryogenic probe surface is in contact with thetissue since catheter electrodes and probes are cylindrical and theheart tissue cannot be visualized clearly with existing fluoroscopictechnology. Further, because of the cylindrical shape, some of theexposed electrode or probe area will almost always be in contact withblood circulating in the heart, giving rise to a risk of clot formation.

[0008] Clot formation is almost always associated with RF energy orcryogenic delivery inside the heart because it is difficult to preventthe blood from being exposed to the electrode or probe surface. Some ofthe RF current flows through the blood between the electrode and theheart tissue and this blood is coagulated, or frozen when a cryogenicprobe is used, possibly resulting in clot formation. When RF energy isapplied, the temperature of the electrode is typically monitored so asto not exceed a preset level, but temperatures necessary to achievetissue ablation almost always result in blood coagulum forming on theelectrode.

[0009] Overheating or overcooling of tissue is also a majorcomplication, because the temperature monitoring only gives thetemperature of the electrode or probe, which is, respectively, beingcooled or warmed on the outside by blood flow. The actual temperature ofthe tissue being ablated by the electrode or probe is usuallyconsiderably higher or lower than the electrode or probe temperature,and this can result in overheating, or even charring, of the tissue inthe case of an RF electrode, or freezing of too much tissue by acryogenic probe. Overheated or charred tissue can act as a locus forthrombus and clot formation, and over freezing can destroy more tissuethan necessary.

[0010] It is also very difficult to achieve ablation of tissue deepwithin the heart wall. A recent study reported that to achieve a depthof ablation of 5 mm, it was necessary to ablate an area almost 8 mm widein the endocardium. See, “Mechanism, Localization, and Cure of AtrialArrhythmias Occurring After a New Intraoperative EndocardialRadiofrequency Ablation Procedure for Atrial Fibrillation,” Thomas, etal., J. Am. Coll. Cardiology, Vol. 35, No. 2, 2000. As the depth ofpenetration increases, the time, power, and temperature requirementsincrease, thus increasing the risk of thrombus formation.

[0011] In certain applications, it is desired to obtain a continuousline of ablated tissue in the endocardium. Using a discrete or pointelectrode or probe, the catheter must be “dragged” from point to pointto create a line, and frequently the line is not continuous.Multielectrode catheters have been developed which can be left in place,but continuity can still be difficult to achieve, and the lesionscreated can be quite wide.

[0012] Because of the risks of char and thrombus formation, RF energy,or any form of endocardial ablation, is rarely used on the left side ofthe heart, where a clot could cause a serious problem (e.g., stroke).Because of the physiology of the heart, it is also difficult to accesscertain areas of the left atrium via an endocardial, catheter-basedapproach.

[0013] Recently, epicardial ablation devices have been developed whichapply RF energy to the outer wall of the heart to ablate tissue. Thesedevices do not have the same risks concerning thrombus formation.However, it is still difficult to create long, continuous lesions, andit is difficult to achieve good depth of penetration without creating alarge area of ablated tissue.

[0014] As noted above, other forms of energy have been used in ablationprocedures, including ultrasound, cryogenic ablation, and microwavetechnology. When used from an endocardial approach, the limitations ofall energy-based ablation technologies to date are the difficulty inachieving continuous transmural lesions, and minimizing unnecessarydamage to endocardial tissue. Ultrasonic and RF energy endocardialballoon technology has been developed to create circumferential lesionsaround the individual pulmonary veins. See e.g., U.S. Pat. No. 6,024,740to Lesh et al. and U.S. Pat. Nos. 5,938,660 and 5,814,028 to Swartz etal. However, this technology creates rather wide (greater than 5 mm)lesions which could lead to stenosis (narrowing) of the pulmonary veins.See, “Pulmonary Vein Stenosis after Catheter Ablation of AtrialFibrillation,” Robbins, et al., Circulation, Vol. 98, pages 1769-1775,1998. The large lesion area can also act as a locus point for thrombusformation. Additionally, there is no feedback to determine when fulltransmural ablation has been achieved. Cryogenic ablation has beenattempted both endocardially and epicardially (see e.g., U.S. Pat. Nos.5,733,280 to Avitall, 5,147,355 to Friedman et al., and 5,423,807 toMilder, and WO 98/17187, the latter disclosing an angled cryogenicprobe, one arm of which is inserted into the interior of the heartthrough an opening in the heart wall that is hemostatically sealedaround the arm by means of a suture or staples), but because of the timerequired to freeze tissue, and the delivery systems used, it isdifficult to create a continuous line, and uniform transmurality isdifficult to verify.

[0015] Published PCT applications WO 99/56644 and WO 99/56648 disclosean endocardial ablation catheter with a reference plate located on theepicardium to act as an indifferent electrode or backplate that ismaintained at the reference level of the generator. Current flows eitherbetween the electrodes located on the catheter, or between theelectrodes and the reference plate. It is important to note that thisreference plate is essentially a monopolar reference pad. Consequently,there is no energy delivered at the backplate/tissue interface intendedto ablate tissue. Instead, the energy is delivered at theelectrode/tissue interface within the endocardium, and travels throughthe heart tissue either to another endocardial electrode, or to thebackplate. Tissue ablation proceeds from the electrodes in contact withthe endocardium outward to the epicardium. Other references discloseepicardial multielectrode devices that deliver either monopolar orbipolar energy to the outside surface of the heart.

[0016] It is important to note that all endocardial ablation devicesthat attempt to ablate tissue through the full thickness of the cardiacwall have a risk associated with damaging structures within or on theouter surface of the cardiac wall. As an example, if a catheter isdelivering energy from the inside of the atrium to the outside, and acoronary artery, the esophagus, or other critical structure is incontact with the atrial wall, the structure can be damaged by thetransfer of energy from within the heart to the structure. The coronaryarteries, esophagus, aorta, pulmonary veins, and pulmonary artery areall structures that are in contact with the outer wall of the atrium,and could be damaged by energy transmitted through the atrial wall.

[0017] Accordingly, it is the object of the present invention to providean improved method and device for making transmural ablations to hearttissue.

[0018] It is a related object to provide a method and device for makingtransmural ablation in heart tissue that minimizes unnecessary damage tothe heart tissue.

[0019] It is a further object to provide a method and device for makingtransmural ablation in heart tissue that creates continuous lesions in asingle step.

[0020] It is still a further object to provide a method and device formonitoring the electrical conductivity of the tissue in the transmurallesion simultaneously with the creation of the lesion.

[0021] It is also an object to provide a method and device for measuringthe temperature of the tissue forming the lesion simultaneously with itscreation.

SUMMARY OF THE INVENTION

[0022] These objects, and others which will become apparent uponreference to the following detailed description and attached drawings,are achieved by the use of a clamping and ablating device for use intreating cardiac arrhythmia having first and second handle members, withfirst and second mating parallel jaw members associated with the firstand second handle members, respectively. The jaw members are preferablycurved and are movable by the handle members between a first openposition and a second clamped position, and the jaw members haveinsulated outer surfaces which may have convex, opposed mating surfaces.Each mating surface has a central region, with the central region of thefirst jaw being aligned with the central region of the second jaw. Afirst elongated electrode extends along the central region of the firstjaw and a second elongated electrode extends along the central region ofthe second jaw. The first and second electrodes are adapted to beconnected to an RF energy source so that, when activated, the electrodesare of opposite polarity. In a preferred embodiment, the electrodes aremade of gold-plated copper and measure between approximately 3 to 8 cmin length and approximately 0.12 to 0.6 mm in width. By the use of sucha device a clamping zone is created that is approximately at least threetimes wider than the contact zone of the electrodes with the tissue.This permits the ablation to be performed with a minimum of contactbetween the electrodes and any blood cells, thus greatly reducing thelikelihood of thrombus. The design also allows for a minimum distancebetween the electrodes, further encouraging complete, transmuralablation that creates a continuous lesion in a single step.

BRIEF DESCRIPTION OF THE DRAWINGS

[0023]FIG. 1 is a schematic view showing a procedure in accordance withthe present invention utilizing ablation elements operatively connectedto either a source of RF energy or cryogenic fluid.

[0024]FIG. 2 is a cross-section of an ablation element for use in thepresent invention taken along lines 2-2 of FIG. 1.

[0025] FIGS. 3-6 show alternate configurations for the ablation elementsof FIG. 2.

[0026]FIG. 7 shows a further step in the inventive procedure in whichtissue is clamped between the ablation elements.

[0027] FIGS. 8-12 schematically illustrate the inventive procedure so asto make a transmural lesion that fully circumscribes a pulmonary vein,with FIG. 9 showing a cross-sectional view of the clamp/ablation elementin contact with the atrial tissue to express blood from the clampedarea.

[0028] FIGS. 13-17 show a further method according to the presentinvention in which transmural lesions are made so as to circumscribeboth pulmonary veins.

[0029] FIGS. 18-22 show a further procedure in which a transmural lesionis made so as to circumscribe a single pulmonary vein.

[0030] FIGS. 23-27 illustrate a further procedure in which a transmurallesion is made so as to circumscribe both pulmonary veins.

[0031]FIG. 28 is a perspective view of a further embodiment of a grasperfor use in an open chest procedure in accordance with the presentinvention showing the grasper in its “closed” position.

[0032]FIG. 29 is a perspective view of the grasper of FIG. 28 with thegrasper in its “open” position.

[0033]FIG. 30 is an enlarged perspective view of the working position ofthe grasper of FIG. 28 with the grasper jaws in the “closed” position.

[0034]FIG. 31 is an enlarged perspective view of the working portion ofthe grasper of FIG. 28 with the grasper jaws in the “open” position.

[0035]FIG. 32 is an enlarged cross-sectional view of the grasper jawsfor the grasper of FIG. 28.

[0036]FIG. 33 is a perspective view of a further embodiment of agrasper, which may be used in either an open or a minimally invasiveprocedure, along with its associated electrosurgical generator.

[0037]FIG. 34 is a side view of the grasper of FIG. 33 showing thegrasper in its “open” position.

[0038]FIG. 35 is an exploded perspective view of the grasper of FIG. 33.

[0039]FIG. 36 is a side cross-sectional view of the grasper of FIG. 33with the grasper jaws in the “open” position.

[0040]FIG. 37 is a side cross-sectional view of the grasper of FIG. 33with the grasper jaws in the “closed” position.

[0041]FIG. 38 is a cross-sectional view taken along line 38-38 of FIG.34 showing the grasper jaws in the “open” position.

[0042]FIG. 39 is a cross-sectional view of the grasper jaws taken alongthe line 39-39 of FIG. 37 showing the grasper jaws in the “closed”position.

[0043]FIG. 40 is a cross-sectional view of the graspers taken along line40-40 of FIG. 34.

[0044] FIGS. 41-51 show alternate constructions for the electrodessuitable for use in the present invention, with FIGS. 41 and 43-51 beingcross-sectional views similar to FIGS. 38 and 39, and FIG. 42 being across-sectional view taken along line 42-42 of FIG. 41.

[0045] FIGS. 52A-K illustrate eleven different ablations to the left andright atrium (as seen from behind in FIG. 52A) and the methods formaking the lesions (FIGS. 52B-K) .

[0046]FIG. 53A is a perspective view of a further embodiment of devicefor performing transmural ablation according to the present invention.

[0047]FIG. 53B is a perspective view of the transmural ablation deviceof FIG. 53A with a portion removed to show detail.

[0048]FIG. 54 is an exploded perspective view of the transmural ablationdevice of FIG. 52.

[0049]FIG. 55 is a longitudinal cross-sectional view of an obturator tipelectrode for use in the device of FIG. 52.

[0050]FIG. 56 is a piercing tip electrode for use in the device of FIG.52.

[0051]FIG. 57 is an enlarged side view of the tip of the instrumentshown in FIG. 52.

[0052] FIGS. 58A-58G illustrate the use of the instrument of FIG. 52 toform a transmural ablation.

[0053]FIG. 59 shows a series of transmural ablations contemplated by theMAZE procedure.

[0054] FIGS. 60A-60I illustrate a procedure for performing acircumferential lesion in lumen such as a pulmonary vein.

[0055]FIG. 61A-61J show the use of the instrument of FIG. 52 for forminga continuous transmural ablation around a pair of pulmonary veins.

[0056]FIG. 62A-I show a further device for performing transmuralablations and the method for making such ablations.

[0057]FIG. 63 is a perspective view of a further embodiment of a grasperadapted for use in minimally invasive procedures.

[0058]FIG. 64 is an enlarged plan view of the handle position of thegrasper of FIG. 63, with portions removed to show detail.

[0059]FIGS. 65A and 65B are enlarged plan views of the jaw actuationmechanism for the grasper of FIG. 63.

[0060] FIGS. 66 is an enlarged fragmentary perspective view of the jawsof grasper of FIGS. 33-40.

[0061] FIGS. 67 is an enlarged perspective view of the tip of the fixedjaw shown in FIG. 66.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0062] With reference to the present invention, the compression of theatrial tissue is important because it insures that the exposed electrodesurface or cryogenic probe is not in contact with any tissue or bloodexcept the clamped tissue to be ablated. Specifically, the clamping ofthe tissue between the electrodes or cryogenic probes insures that theconductive or cooled area is only in contact with the clamped tissue.The compressed tissue acts to isolate the electrically active orcryogenically cooled surface, and prevents inadvertent energy deliveryto other parts of the heart or blood. The outside temperature of theelectrode can easily be monitored to insure that the temperature of theinsulation in contact with blood remains below a critical temperature(40° C., for example).

[0063] In one form of the invention, transmural ablation using RF energyis accomplished by providing an atrial ablation device having a lower“j” clamp/electrode element and placing it on the atrial tissue belowthe pulmonary veins.

[0064] Once the pulmonary veins have been isolated, an upperclamp/electrode element is introduced, and the clamp assembly “J” isworked back onto the epicardial atrial tissue. Once the jaws arepositioned below the ostia of the pulmonary veins, the tissue ispartially clamped, allowing continued flow from the pulmonary veins tothe left atrium. Once the clamps are safely away from the pulmonary veintissue, and onto atrial tissue, the clamps are closed together tocompress the tissue. Once the tissue is compressed, bipolar RF energy isused to ablate the clamped atrial tissue. The clamps are then removed,the lesion having been created. Lesions may also be created by insertingone clamp/electrode element through an incision in the heart so as topermit contact with endocardial tissue. This incision may be createdwith a separate instrument. Alternatively, the tip of one of the jawsmay have a piercing structure associated therewith for making the entryincision. Once the clamps are properly located, the tissue is compressedand RF energy is applied.

[0065] Turning now to the figures of the drawings, a method embodyingthe present invention is shown schematically in FIG. 1. A clamping typedevice 10 is provided to group the two walls 22, 24 of the atrium 20,and delivers bipolar RF energy through both walls held between the twoupper and lower clamp jaws 50, 51. FIG. 1 shows the upper and lowerparallel clamp jaws 50, 51 and electrodes 52, 53 positioned above andbelow atrial tissue 22, 24, distal to the pulmonary veins. FIG. 2,Section 2-2 of FIG. 1, shows a cross-section of the clamping memberincluding the insulator 28 and electrode 53. Alternate configurations ofthe clamping members are shown in FIGS. 3-6. FIG. 3 shows a crosssection of the electrode consisting of an insulating layer 11, and aconductive strip 12. The electrode of FIG. 3 may be constructed of atungsten wire as the conductive material 12, with polyamide as theinsulating material 11. The conductive strip is created by exposing apart of the tungsten wire through the polyamide. FIGS. 4 and 5 show analternate electrode construction consisting of a carbon fiber element13, and an insulating material 14, such as ABS. The conductive strip 15may be comprised of a copper/gold electrode plated onto the ABS. FIG. 6shows a cross section of yet another possible electrode design where theconductive material 16 consists of a stainless steel needle with lumen17 and insulating material 18.

[0066]FIG. 7 shows the parallel jaws 50, 51 clamping and ablating theatrial tissue 20 distal to the pulmonary veins 26. Proximal point A isclamping and ablating the atrial tissue distal to the pulmonary veins.Proximal point A is the most proximal point of ablated tissue on boththe upper and lower atrial wall. Distal point B is the most distal pointof ablated tissue on both the upper and lower atrial wall.

[0067] FIGS. 8-12 show the inventive procedure that fully circumscribesa pulmonary vein with transmural lesions. FIG. 8 shows a top view of theinstrument jaws positioned for a 2-step isolation of a single pulmonaryvein. The lower jaw is directly beneath the upper jaw, and is not shown.Proximal point A and distal point B correspond to FIG. 7.

[0068]FIG. 9 shows a cross-sectional view of the jaws clamping andablating atrial tissue. Importantly, FIG. 9 shows that theelectrode/clamp configuration provides a clamped zone of tissue that iswider than the zone of ablated tissue. This is achieved by using anelectrode width that is narrower than the clamped tissue width, andpreferably less than one-third of the clamped tissue width. As shown inFIG. 9 (and better illustrated in FIG. 26), the electrode forms the apexof the triangular clamping member. Other convex shapes are alsocontemplated.

[0069] The wider zone of clamped tissue serves several purposes. Whenthe clamping members are closed onto tissue, any blood in the clampedzone is squeezed or expressed out. Further, the distance between theelectrodes is minimized, so that the ablation zone remains narrow. It isimportant to isolate the blood from the ablation zone to avoid creatingthrombus. Accordingly, a clamped zone that isolates the ablation zonefrom the blood minimizes the temperature at the periphery of theablation zone and will reduce the likelihood of the formation ofthrombus by the blood in contact with the clamped zone.

[0070] Once tissue has been fully ablated with the clamp in the positionshown in FIG. 8, an ablation line of tissue on both upper and loweratrial walls is created. This is shown as ablation line 60 in FIG. 10.The clamp is then repositioned to the position shown in FIG. 10, so thatthe distal point D overlaps the ablation line 60. The tissue is clampedand ablated as shown in FIGS. 7 and 9, and a second ablation line 61(FIG. 11) is formed on both the upper and lower atrial walls. Proximalpoint C and distal point D correspond to points A and B respectively.The full ablation line is shown in FIGS. 11 and 12 with points A-D asshown.

[0071] This “clamping” method and device for creating transmural lesionshas a number of advantages. First, using a two step method as shownallows for clamping and ablation of atrial tissue without stopping theblood flow from the pulmonary vein. Secondly, by clamping both wallstogether, and delivering energy through the clamped tissue, the atrialtissue is not penetrated. Because the atrial tissue is not penetrated, alarger jaw can be used, and the clamping force can be much higherbecause of the increased stiffness of the jaw. Also, there is no concernof bleeding from an atrial puncture.

[0072] Another advantage of this method and device is that ablation oftissue within the pulmonary veins is avoided, as recent articles haveshown that ablation of tissue within the pulmonary veins can causepulmonary hypertension and stenosis. Specifically referring to FIGS.13-17, a longer jaw could be used to create an ablation line throughatrial tissue which electrically isolates both pulmonary veins using thesame method.

[0073] FIGS. 18-22 show the clamping device in a curved-jaw embodimentthat creates a circumferential lesion around the pulmonary vein in onestep. FIGS. 18 and 19 show the clamp jaws positioned around thepulmonary vein. FIGS. 20 and 21 show the device clamping and ablatingatrial tissue distal to the pulmonary vein. FIG. 22 shows the resultingablation line 60.

[0074] FIGS. 23-27 show the same concept applied to a device and methodfor creating a lesion around both pulmonary veins. The advantage of thisconcept is that the entire lesion is created in one step. Thedisadvantage is that blood flow from the pulmonary vein(s) is cut offduring ablation. Using a curved electrode also allows the user to ablatetissue more distal to the pulmonary vein than would be possible with astraight electrode. Note that this curved type electrode could be usedwith a two step procedure as described above, using “left” and “right”curved devices to create a lesion which was more distal to the pulmonaryveins. Note also that this method and device are not limited to usearound the pulmonary veins, but could be used anywhere in the atriumthat the clamp could be applied.

[0075] Turning to FIGS. 28-32, there is seen a further version of acardiac grasper 70 suitable for an open chest procedure in accordancewith the present invention. The grasper 70 includes two ring handles 72,74 joined together for relative movement by a pivot screw or pin 76.Each handle 72, 74 has a jaw member 78, 80 respectively associatedtherewith, each jaw being curved so that it has a major portion that issubstantially perpendicular to the handles. This gives the grasper 70 anL-shaped appearance, with a working portion of the jaws being betweenapproximately 3-8 cm in length.

[0076] The grasper is made of a rigid material, such as stainless steel,and is substantially encased in a durable insulating material, such asABS plastic. With reference to FIG. 32, which shows the opposed jawmembers in cross section, the stainless steel structural support isdesignated 82. The structural support 82 is completely encased byinsulating members 84, 86 and 88. The tips 78 a, 80 a of the jaws may bemade of a soft, atraumatic material in order to reduce the likelihood ofunintentional injury of tissue by the jaws.

[0077] In keeping with the invention, the grasper jaws have raised orconvex, opposed tissue clamping surfaces, 90, 92, respectively, witheach clamping surface, 90, 92 centrally supporting an electrode 94, 96,respectively, of opposite polarity. RF energy of opposite polarity issupplied to the electrodes 94, 96 through conductors 98, 100, which areconnected to an RF generator. As with the previously-described jawmembers, this electrode/clamp configuration provides a clamped zone oftissue that is significantly wider than the zone of ablated tissuecreated by the opposed electrodes. This causes for any blood in theclamp zone to be squeezed or expressed out of the ablation zone, thusreducing the likelihood of thrombus formation, as well as minimizing thedistance between the electrodes, so that the ablation zone remainsnarrow. The clamping also eliminates the cooling effect of circulatingblood.

[0078] With reference to FIG. 32, the electrodes 94, 96 have a T-shapedcross section, with the cross portion of the T resting on the insulatingmember 88 and the upright portion of the T protruding through a narrowopening in the insulating member 84, thus creating an exposed electrodesurface that contacts the tissue grasped between the jaws. In practice,the electrodes are preferably made of gold-plated copper and extendalong substantially the entire working surface of the jaw members. Theexposed portions of the electrode are generally less than 1.25 mm inwidth, and preferably between approximately 0.12-0.6 mm in width. Thisinsures that most of the jaw surface is insulator, and that theelectrode comprises generally less than one-third of the width of thejaw.

[0079] In keeping with a further aspect of the invention, the graspersmay provide feedback that permits the user to gauge the completeness(i.e., degree of transmurality) of the ablation. Specifically, atransmural lesion blocks electrical signals because it is non-conductivescar tissue. Because impedance is simply the inverse of conductivity,the ability of the lesion to block electrical signals is accuratelyindicated by its impedance, which can be measured simultaneously withthe creation of the lesion. During RF energy application to the tissueto be ablated, the current and voltage applied to the tissue aremeasured, and the impedence calculated and stored. Based upon a functionof the impedence (e.g., its value, the change in value, or the rate ofchange in value)) it is determined whether ablation is complete andtransmural. See e.g., U.S. Pat. No. 5,403,312, which is incorporated byreference herein. Indicator lights or other types of signals (e.g.,audible may be associated with the grasper to correspond to the degreeof ablation determined by the impedence feedback system. For example,once the impedence reaches a certain level for a certain period of time,a red light may be activated to signal that ablation is complete.

[0080] In keeping with another aspect of the invention, a feedbacksystem for determining the temperature of the ablated tissue is alsoprovided. To this end, the jaws include a series of thermocouples 102that are supported in the insulating member 84 remote from theassociated electrode 94 near the edge of the jaw 78. The thermocouples102 protrude slightly through the surface of the insulating member 84 soas to engage any tissue clamped between the jaws 72, 74. Wires 104 areattached to the thermocouples 102 to transmit the information receivedto a remote location. Again, a visual or other indicator may be providedto alert the user that a certain pre-determined critical temperature(e.g., 40° C.) has been reached, thus permitting the user to avoidundesired thermal spread.

[0081] Turning to FIGS. 33-37, there is a further version of a cardiacgrasper 110 suitable for both open and minimally-invasive procedures inaccordance with the present invention. As seen in FIG. 33, the grasper110 includes a cord 112 for housing the conductors (not shown) and forplugging into an electrosurgical generator 114 to provide current to thegrasper 110. As discussed above, the generator 114 includes a display115 to provide a simultaneous visual indication of the degree ofconductance of the tissue being ablated. The instrument 110 includesopposed parallel, curved jaw assemblies 116, 118 with jaw assembly 116being fixed and jaw assembly 118 being movable between an open position(as seen in FIGS. 34 and 36) to a closed position (shown in FIG. 37).The fixed jaw assembly 116 comprises a fixed electrode 120, a fixedinsulator 122 and a fixed jaw cap 124. The fixed electrode 120 providesan electrical pathway adjacent to the tissue to be ablated and islocated on the inside of the fixed jaw assembly 116 (the “inside” beingdefined as the side that contacts the tissue to be ablated). The fixedinsulator 122 surrounds the fixed electrode 120 and forms the inside ofthe fixed jaw assembly 116. The fixed jaw cap 124 forms the backside ofthe fixed jaw assembly 116 (the “backside” being defined as the surfaceopposite the fixed electrode 120).

[0082] The drive jaw assembly 118 comprises a drive electrode 126, adrive insulator 128, and a drive jaw cap 130. The drive electrode 126provides a second electrical pathway adjacent the tissue to be ablatedand is located on the inside of the drive jaw assembly 118 (“inside”being defined as the side contacting the tissue to be ablated) . Thedrive insulator 128 surrounds the drive electrode 126 and forms theinside of the drive jaw assembly 118. The drive jaw cap 130 forms thebackside of the drive jaw assembly 118 (“backside” being defined as thesurface opposite the drive electrode 126).

[0083] Each of the electrodes 120, 126 is attached to an electricallyconductive means, such as a wire, that runs the length of the extensionshaft and through the conductor cord 112 for coupling to the RFgenerator 114.

[0084] Each jaw assembly 116, 118 is supported by a two piece extensionshaft comprising a right fixed member 132 and left fixed member 134 (forthe fixed jaw) and a right drive member 136 and left drive member 138(for the drive jaw 118). A shaft cap 139 covers the coextensive portionsof the fixed members 132, 134 and the drive members 136, 138 (when thejaws are in the open position as seen in FIG. 34). The right fixedmember 132 and left fixed member 134 combine to form a structure thatextends from a handle 140, through the shaft cap 139, and thenterminating at the distal end of the instrument 110 in the fixed jawassembly 116 on the right and left sides, respectively, of theinstrument. Similarly, the right drive member 136 and left drive member138 extend from the handle 140, through the shaft cap 139, and thenterminate in the drive jaw assembly 118 on the right and left sides,respectively, of the instrument. The portions of the fixed members 132,134 co-extensive with the fixed jaw assembly 116 are joined by a fixedbridge 142 along the length of the jaw. Similarly, the portions of thedrive members 136, 138 co-extensive with the drive jaw assembly 118 arejoined together by a drive bridge 144 along the length the drive jaw118.

[0085] The handle 140 comprises two mating halves 140 a, 140 b forencapsulating the actuation and force control mechanisms for thegrasper, as well as providing for grounding of the shaft components bymeans of a conductive shaft pin 141. In order to move the drive jawassembly 118 between its open and closed positions, the handle 140includes a lever comprising a pair of lever plates 146 and a levershroud 148. The lever is pivotally mounted on a support member 150extending between the two halves 140 a, 140 b of the handle 140, with alever spring 151 biasing the lever to its open position (FIG. 34). Thelever plates 146 are coupled by a lever pin 152 to a carriage 154 thatcaptures the proximal ends of the drive members 136, 138, so as toprovide translational motion to these members.

[0086] The carriage 154 includes a lost motion assembly comprising acarriage spring 156 for controlling the minimum and maximum loads thatcan be applied to tissues that are to be captured between the jawassemblies 116, 118. As can be readily appreciated, the thicker thetissue that is grasped between the jaws, the greater the compression ofthe spring 156, and the greater the compression force exerted by thejaws on the tissue. (The range of tissue thickness is expected to bebetween about 1-15 mm.) Adjustment of the compression force isaccomplished by pre-loading the carriage spring 156 with a loadadjustment screw 158. The lost motion assembly also includes a thumblatch 160 for releasing the clamping pressure and for providing amechanical stop for the spring-loaded carriage 154. The thumb latch 160is pivotally mounted on a latch pin 162 to secure the thumb latch to thehandle 140. Additionally, a latch spring 164 is provided for biasing thethumb latch 160 to its locked position. A latching step on the carriage154 interfaces with the tip of the thumb latch 160 to provide for themechanical stop.

[0087] When the lever is pivoted with respect to the handle 140, thedrive jaw assembly 118 and its drive members 136, 138 slide along thelongitudinal direction of the shaft to bring the two jaw assemblies 116,118 into contact with the tissue intended to be grasped.

[0088] In order to ablate a narrow, long region of biological tissuewith the instrument 110, the tissue is first placed between the openinstrument jaws 116, 118. The user then grasps the actuation levercomprising the lever plates 146 and lever shroud 148 to apply the forcerequired to drive the drive members 136, 138 and drive jaw assembly 118distally, thus compressing the tissue and automatically engaging thethumb latch 160. The thumb latch 160 locks the position of the drivemembers 136, 138 and the drive jaw assembly 118 with respect to thehandle 140 and the fixed jaw assembly 116. The amount of jaw force onthe tissue is controlled by the lost motion assembly between the leverand the drive members 136, 138.

[0089] With the jaws closed on the tissue, the operator activates the RFgenerator 114. RF energy passes through the tissue between theelectrodes 120, 126, thus ablating the tissue between these electrodes.After completion of the ablation cycle, the operator releases theclamping of the tissue by depressing the thumb latch 160, thus releasingthe carriage 154. With the carriage 154 released, the lever spring 151drives the drive members 136, 138 and the drive jaw assembly 118proximally to their open positions. The actuation lever, since it isdirectly coupled to the carriage 154, also returns to the open position.

[0090] Turning to FIGS. 41-51 there is seen in schematic form variousconfigurations for the electrodes 120, 126 for use in conjunction withthe grasper 110. Each of FIGS. 41 and 43-51 show a cross-section throughthe instrument jaws as clamped on the tissue to be ablated. Eachelectrode is formed of a piece of electrically conductive metal that maybe plated with a biocompatible material.

[0091] With reference to FIGS. 41 and 42, the electrode geometryconsists of a largely rectangular electrode with a window of materialremoved from the central region. The window area is filled with theinsulator material 122, 128. At the clamping surface the electrodeinsulator material leads away from the electrode on a radius. Theelectrode material protrudes outside the clamping surface of theinsulating material. However, the electrode may also be flush with theclamping surface.

[0092] With reference to FIG. 43, the electrode geometry is largelyrectangular and the electrode insulator material leads away from theelectrode on a radius. The electrode is flush with the clamping surfaceof the insulator material.

[0093] With reference to FIG. 44, the electrode is applied to fill agroove in the insulator material by way of a plating process. Theelectrode geometry is largely rectangular and the electrode insulatormaterial leads away from the electrode on a radius. The electrodeplating is largely flush with the clamping surface of the insulatormaterial.

[0094] With reference to FIG. 45, the electrode is formed into aU-shaped element. The electrode insulator material leads away from theelectrode on a radius. As shown, the electrode material extends outsidethe clamping surface of the insulator material. However, the electrodematerial may also be flush with the insulator clamping surface.

[0095] With reference to FIG. 46, the electrode is applied to fill agroove in the insulator material by way of a plating process, with theelectrode geometry being largely rectangular. The electrode insulatormaterial creates a small flat surface perpendicular to the closure planethat is largely flush with the surface of the plate or electrode. Asshown, the electrode material is flush with the clamping surface of theinsulator material. However, the electrode material may also be appliedso that it extends outside the insulator clamping surface.

[0096] With reference to FIG. 47, the electrode geometry is largelyrectangular and the electrode insulator material leads away from theelectrode on a radius. The electrode material extends outside theclamping surface of the insulator material.

[0097] With reference to FIG. 48, the electrode configuration is againlargely rectangular, with the electrode insulator material creating asmall flat surface perpendicular to the closure plane that is largelyflush with the surface of the plate or electrode. The electrode is flushwith the clamping surface of the insulator material and a temperaturesensing means, such as a thermocouple 166 (see also FIGS. 35 and 39), ispositioned in close proximity to the electrode, but electricallyisolated from the RF energy.

[0098] With reference to FIG. 49, the electrode is applied to fill agroove in the insulator material by way of a plating process. Theelectrode geometry is largely rectangular and the electrode insulatormaterial leads away from the electrode on a radius.

[0099] With reference to FIG. 50, the electrode is applied to thesurface of the electrode insulator material by way of a plating process.The electrode geometry is largely rectangular with the electrodeinsulator material leading away from the electrode on a radius. Theelectrode plating is largely flush with the clamping surface of theinsulator material. With reference to FIG. 51, the electrode is roundwire made from an electrically conductive metal that may be plated witha biocompatible material. The electrode insulator material leads awayfrom the electrode on a radius. As shown, the electrode material extendsoutside the clamping surface of the insulator material. However, theelectrode material may also be flush with the insulator clampingsurface.

[0100] A further embodiment of a grasper according to the presentinvention is shown in FIGS. 63-65 and is designated generally 250. Thegrasper 250 has jaws 252, 254 similar in structure to those describedabove in connection with the embodiments of FIGS. 28-32 and 33-40, butincludes a different actuation mechanism. Specifically, the jaws 252,254 of the grasper 250 are biased so that they are normally in theclosed position, the jaws being moved to the open position by moving thetwo handle members 256, 258 towards each other. This action serves towithdraw a push-rod 260 (FIG. 64), which is pivotally connected to thehandle members 256, 258 by links 262, 264. With reference to FIG. 65Aand FIG. 65B. The distal end of the push rod 260 includes two pins 266,268 which are captured in slots 270, 272 in their respective jaw members252, 254. When the pins 266, 268 are located in the distal ends of theslots 270, 272, the jaws are in the closed position. The jaws 252, 254open as the pins 266, 268 move proximally in the slots 270, 272 throughthe withdrawal of the push rod 260 by the closing of the handle members256, 258.

[0101] The jaws 252, 254 also include a lost motion connection includinga spring to bias the jaws toward the closed position. With referenceagain to FIG. 65A and FIG. 65B, the jaws 252 and 254 are pivotallyconnected to each other by means of a pin 274. The pin 274 is secured tothe jaw member 254, but is received in an elongated slot 276 in jawmember 252. The pin 274 is biased to the top of the slot 276, thusbiasing the jaws 252, 254 to the closed position, by means of a leafspring 278 having one end secured to the pin 274 and the other endcaptured between two studs 280, 282 carried on the jaw member 252.

[0102] FIGS. 52A-K illustrate a series of 11 different lesions orablations that may be made using either an open or a minimally invasivetechnique with the graspers described above. Turning first to FIG. 52A,there is seen a view of the heart showing the right and left atriums (asviewed from behind). The heart includes the left atrial appendage (LAA)and the right atrial appendage (RAA). The right pulmonary veins (RPVs)and left pulmonary veins (LPVs) enter into the top of the left atrium.The superior vena cava (SVC) and inferior vena cava (IVC) are alsoshown. The mitral valve annulus is designated as MVA, while thetricuspid valve annulus designated TVA. In FIG. 52A, 11 differentlesions are indicated by the reference numerals 1-11. A method formaking each of these lesions is illustrated in the following FIGS.52B-K. It should be appreciated that, depending upon a particularpatient's indications, the lesions 1-11 may be created in a variety ofcombinations.

[0103] With reference to FIG. 52B, a method for making lesion 1 tocircumscribe the right pulmonary veins (RPVS) is shown. This lesion ismade completely epicardially in a manner similar to that illustrated inFIGS. 23-27. FIG. 52C illustrates lesion 2, an epicardial ablation thatfully circumscribes the left pulmonary veins (LPVs). Again, this lesionmay be made in a manner similar to that illustrated in FIGS. 23-27.

[0104]FIG. 52D illustrates a method for making lesion 3, which connectslesions 1 and 2. Lesion 3 is made with only one of the jaws of thegraspers being located epicardially. The mating jaw is inserted into theinterior of the heart through a small incision which is sealed using apurse-string suture. The incision as illustrated is made interior thelesion 1 encircling the right pulmonary veins (RPVs).

[0105] Lesion 4 connects the lesion 1, which surrounds the rightpulmonary veins, to the mitral valve annulus (MVA). It may be madethrough the same incision and purse-string suture used for making lesion3. With reference again to FIG. 52D, the jaws of the grasper are merelyrotated down so that the distal end of the jaw overlies the mitral valveannulus.

[0106] When making lesion 4, care must be exercised in locating thegrasper jaws so that the electrodes, when RF energy is applied, do notdamage the mitral valve leaflets. It is known that the electricalsignals generated by atrial tissue differ from the electrical signalsgenerated by ventricular tissue. Consequently, the distal tip of one ofthe jaw members of the grasper includes an EKG sensor so that the EKG ofthe tissue contacted by the tip of the grasper can be monitored.

[0107] As best seen in FIGS. 66 and 67, the distal tip of the fixed jaw116 includes a pair of laterally-opposed bipolar EKG electrodes orsensors 168 spaced slightly distally from the distal-most end of theelectrode 120. The sensors 168 are connected to conductive leads 170(FIG. 33) that are adapted to be connected to an EKG monitor (not shown)to provide a display of the EKG. Thus, as the jaws of the grasper arerotated downwardly after making lesion 3, the surgeon can constantlymonitor the EKG, looking for the change from an atrial EKG to aventricular EKG, to facilitate accurate placement of the jaw tip on themitral valve annulus, and away from the mitral valve leaflets.

[0108] It may also be desirable to make a lesion between the superiorvena cava (SVC) and the inferior (IVC). This may be created in twosteps, in which lesions 5 and 6 are made. With reference to FIG. 52E, anincision with purse-string suture is made approximately midway betweenthe SVC and IVC, with one of the jaws of the grasper being inserted intothe incision so as to have its end adjacent the base of the SVC. Thelesion 5 is formed and then the instrument is rotated 180° as shown inFIG. 52F, to make lesion 6. Lesion 7 may conveniently be made throughthe same incision and purse-string suture as lesions 5 and 6, as shownin FIG. 52G. Lesion 7 extends from between the SVC and IVC out towardthe right atrial appendage (RAA).

[0109] A lesion 8 is made between the right atrial appendage and thetricuspid valve annulus (TVA) utilizing an incision and purse-stringsuture made in the RAA, as illustrated in FIG. 52H. Lesion 8 is made onthe opposite side of the right atrium as lesion 7, and thus is shown indotted line in FIG. 52A. A lesion 9 may also be made circumscribing theright atrial appendage so as to intersect both lesions 7 and 8. As shownin FIG. 52I, lesion 9 is made epicardially. A similar epicardialablation circumscribing the left atrial appendage is designated 10 andillustrated in FIG. 52J.

[0110] A final lesion 11 is illustrated that connects lesion 10circumscribing the left atrial appendage with lesion 2 thatcircumscribes the left pulmonary veins. As illustrated, the lesion 11 ismade utilizing an incision and purse string suture through which thegrasper jaw is introduced, the incision being located in the left atrialappendage beyond the lesion 10.

[0111] In a further embodiment, the present device consists of two long,linear, wire-type electrodes, which are in parallel relationship to eachother, each approximately 1 mm in diameter, and 50 mm long. Theelectrodes are insulated along their entire surface with a thin layer ofhigh dielectric material such as polyamide, except for a thin strip ofelectrically conductive material that runs along the length of eachelectrode, in face-to-face relationship with each other. The electrodesare comprised of a high modulus material, such as tungsten or carbonfiber.

[0112] One of the electrodes is designed to be introduced into theinterior of a hollow organ through a small puncture wound in the wall ofthe organ. The second electrode is introduced on the opposite side ofthe hollow organ wall. The device incorporates a mechanism for advancingeach electrode individually, or both simultaneously, in parallelrelation with each other. The device also includes a clamping mechanismthat brings the two electrodes together so that their exposed conductivesurfaces are in face-to-face relation and the electrodes exertsufficient pressure to clamp the tissue. Once both electrodes have beenadvanced to their desired positions, the clamping mechanism is activatedwhich brings the two wires together, and clamps the tissue between thetwo exposed electrode surfaces. RF energy is then applied between thetwo electrodes, and the tissue is ablated in a long, continuous,transmural line. A monitoring device measures the voltage, current,impedance, and/or temperature between the two electrodes, and analgorithm determines whether the tissue is fully ablated.

[0113] This device provides a way to achieve and verify a fullytransmural and continuous line of tissue ablation by locating the atrialtissue between two bipolar wire electrodes, and clamping the tissue. Theforceps consist of two electrode pads of opposite polarity designed tograsp and clamp tissue. A well-known method of determining the status ofthe tissue between the electrode pads is to monitor the current,voltage, and impedance of the tissue, as done using the Richard Wolfgenerator for bipolar forceps. It is well known in the art that theablative status of tissue clamped between two bipolar electrodes caneasily be determined by monitoring the increase in tissue impedance asthe tissue dessicates.

[0114] This device is to be used with an RF generator that monitorscurrent, voltage, and impedance to determine the state of tissueablation of the tissue compressed between the inner and outerelectrodes. The RF generator will be equipped with an indicator whichinforms the user of the status of the clamped tissue, and when ablationis complete (i.e., transmural along the entire length of theelectrodes).

[0115] This device provides the capability of creating long, transmurallesions through atrial wall tissue of varying thickness because itemploys an active bipolar electrode on each side of the atrial wall, andthe ablation proceeds from both the inside and outside of the atrialwall. The device is also unique in that the electrodes are used tocompress the tissue to be ablated. This compression is critical becausethe inside and outside surfaces of the atrium can have irregularities,and a high clamping pressure insures that both electrodes are makinggood contact with tissue along the full length of each electrode.Clamping the tissue also reduces the distance between the electrodes,and makes the ablation more efficient because the electrical energy ismore concentrated. Because of this higher concentration of energy, lowerpowers and temperatures can be used to achieve complete ablation, andthe process is considerably faster.

[0116] As an example, to fully ablate a 5 mm deep lesion, 30 cm long cantake several minutes with an endocardial catheter electrode array, andthe temperatures can be as high as 80 to 90 degrees centigrade at thetissue surface with the generator power as high as 40 to 50 watts. Inbenchtop testing of the present invention in animal hearts, a fullytransmural 30 mm line through 5 mm of tissue was achieved in 5 secondsat 20 watts.

[0117] With reference to FIGS. 53-54, a further embodiment of the deviceis shown. The device consists of an inner wire electrode wire electrode201, an outer wire electrode 202, an inner slider button 203, an outerslider button 204, and a clamping slider tube 205 and button 206. Thedevice body 207 houses the wire electrodes, slider tube and buttons,connector wires 207 a and 208, and bipolar connector 209. The device mayalso include slit needle introducer tip 210.

[0118] The operation of the device begins by advancing the innerelectrode wire 201 by advancing the slider button 203. Once the innerelectrode 201 is advanced to the desired length, the outer electrode 202is advanced by advancing slider button 204. Note that furtheradvancement of slider button 204 also advances slider button 203, sothat both electrodes 201 and 202 advance simultaneously. Because of thebend 202 a in the electrode wire 202, and the notch 205 a in the slidertube assembly 205, the slider tube advances along with the outerelectrode 202. Once both electrodes are advanced to the desired length,the slider tube 205 is advanced so that the end 205 b of the slider tube205 contacts the arcuate wire segment 202 b of electrode wire 202.Further advancement of slider tube 205 acts to compress the electrodewires 201 and 202 together along the entire effective length L.

[0119]FIGS. 55 and 56 show two types of electrode wires, a piercing tip(FIG. 56), and an obturator, or blunt tip (FIG. 55). The electrodes maybe similar in construction to those shown in FIGS. 2-6, which aredescribed above. FIG. 57 shows a side view of the instrument tip.

[0120]FIG. 58A shows the instrument used to penetrate the wall of ahollow organ, such as the heart. The slit needle 210 penetrates tissuethrough the wall of the atrium 218. In FIG. 58B, the inner wireelectrode 201 is advanced through the puncture wound into the interiorof the atrium. In FIG. 58C, the outer needle 202 is initially advancedonto the external surface of the atrial wall 218. FIG. 58D shows theinner 201 and outer 202 needles as they are simultaneously advancedalong the inner and outer surfaces of the atrial wall 218. FIG. 58Eshows the pusher tube 205 advanced to compress the tissue of the atrialwall 218 at location 219. RF energy is then applied between theconductive strips 212 on each electrode to ablate the compressed tissue219. FIG. 58F shows section B-B of FIG. 58E, with the inner 201 andouter 202 electrodes compressing the tissue 219. The area of ablatedtissue is shown as 220. The alternate electrode configuration of FIG. 5is shown in FIG. 58G. Blood cells are represented as 221.

[0121] The compression of the tissue is important because it insuresthat the exposed electrode surface is not in contact with any tissue orblood except the clamped tissue to be ablated. Referring to FIGS. 58Fand 58G one can see that the clamping of the tissue between theelectrodes insures that only the conductive area is in contact with theclamped tissue. Especially important is avoiding any contact between theconductive area of the electrode and blood in the atrium. Contactbetween an active electrode and blood in the atrium is major cause ofthrombus formation in ablation procedures. The compressed tissue acts toisolate the electrically active surface, and prevents inadvertent energydelivery to other parts of the heart or blood. The outside temperatureof the electrode can easily be monitored to insure that the temperatureof the insulation in contact with blood remains below a criticaltemperature (40° C., for example).

[0122]FIG. 59 shows a potential series of continuous transmural ablationlines 222 located around the pulmonary veins 223 in the left atrium 224.A series of puncture wounds 225 are shown as one means to achieve thepattern of ablation lines (shown in dot-dash lines).

[0123]FIG. 60A shows a method for achieving a circumferential lesion ina pulmonary vein 223. The inner needle 201 is a piercing tip as shown inFIG. 56. The needle is advanced completely through the wall of thepulmonary vein until it exits the vein. In FIG. 60B, the outer electrode2 is advanced parallel to the inner electrode 201. In FIG. 60C, theelectrodes are compressed, and the compressed vein wall tissue 226 isablated by applying RF energy between the two electrodes. In FIG. 60D,the electrodes are released, and the vein wall tissue 226 returns to itsoriginal shape. FIG. 60E shows the outer electrode 202 retracted backinto the instrument body, and the instrument is rotated 180 degreesabout the axis of electrode 201.

[0124]FIG. 60F shows the outer electrode 202 advanced along the oppositeside of the pulmonary vein from the ablated tissue 220. In FIG. 60G, theelectrodes are compressed, and the compressed vein wall tissue 227 isablated by applying RF energy between the electrodes. FIG. 60H shows theposition of the electrodes with the pusher tube retracted, and the fullycircumferential lesion 220. FIG. 60I shows the instrument retracted fromthe vein, and the circumferential lesion of ablated tissue 220.

[0125] FIGS. 61A-61J show the instrument used in a method to create acircumferential lesion around a pair of pulmonary veins 226 and 227. InFIG. 61A the inner electrode 201 is advanced into the side of the atrialwall 218, just below the ostium of the pulmonary vein 226 by advancingslider button 203. FIG. 61B shows electrode 201 and slider 203 fullyadvanced, and exiting the atrial tissue 218 just below the ostium ofpulmonary vein 227. FIG. 61C shows outer electrode 202 advanced fully inparallel and to the same length as inner electrode 201 by advancingslider 204. Note that slider tube button 205 has advanced to itsintermediate position.

[0126]FIG. 61D shows slider button 205 fully advanced, which clampselectrodes 201 and 202 together just below the ostia of the pulmonaryveins on the side of the veins indicated by tissue surface 218 a, andcompresses the atrial wall tissue. RF energy is then applied between thetwo electrodes, and the clamped tissue 219 is ablated. In FIG. 61E,electrode 202 is retracted by retracting slider button 4. The line ofablated tissue is shown as 219 a. This line of ablated tissue 219 a willbe completely continuous and transmural, and connect inner needle entrypoint 229 with inner needle exit point 230 and extend along the side ofthe atrial wall.

[0127]FIG. 61F shows the device body 207 rotated 180 degrees about theaxis of the inner electrode 201 so that the atrial surface 218 b on theopposite side of the pulmonary veins is exposed. FIG. 61G shows sliderbutton 204 and outer electrode 202 advanced over the opposite surface ofthe atrium 218 b. FIG. 61H shows slider button 205 advanced, and theelectrodes 201 and 202 clamping the tissue 219 b just below the ostia ofthe pulmonary veins 226 and 227 along atrial wall 218 b. RF energy isthen applied between the electrodes 201 and 202 to ablate the compressedtissue 219 b. In FIG. 61I the slider button 205 is retracted, and theelectrodes release the tissue 219 b. The outer electrode is thenretracted, exposing the tissue 219 b that is now fully ablated asindicated by the line 219 b. FIG. 16J shows a top view of FIG. 61Ishowing the continuous line of ablated tissue surrounding pulmonaryveins 226 and 227, connected by entry point 229 and exit point 230 ofinternal electrode 201. The electrode is then retracted, leaving acontinuous transmural lesion that electrically isolates the pulmonaryveins from the rest of the atrial tissue.

[0128] In another embodiment of the invention, a penetratingcompressive/tensile electrode is used. Once the jaws are positionedbelow the ostia of the pulmonary veins, the tissue is partially clamped,allowing continued flow from the pulmonary veins to the left atrium. Anelectrode needle is introduced which enters the left side of the atrialtissue and exits on the right side into a tip securing point on thelower jaw. This point will prevent the tip from moving axially when aneedle is pushed. The lower atrial tissue can be compressed by “pushing”on the needle with a force that compresses tissue between the needleelectrode and the lower jaw electrode. Bipolar RF energy is then appliedbetween the needle and lower jaw electrodes to ablate a line of tissuefrom the needle entry to exit point.

[0129] Once the lower atrial tissue has been ablated, the upper jaw ismoved down to contact the tip of the lower jaw. Note that this stillprovides an open lumen for blood flow from the pulmonary veins to theleft atrium. The needle is rotated 180 degrees on its axis so that theelectrode surface faces up. The needle is then “pulled” to createtension, and exert a compressive force that compresses tissue betweenthe needle electrode and the upper jaw. Bipolar RF energy is thenapplied between the needle electrode and upper jaw to ablate the tissue.Note that the partial closing of the upper jaw to contact the tip of thelower jaw could be done prior to compressing the lower atrial tissue.

[0130] With reference to FIGS. 62A-62I the clamping apparatus asgenerally described above is shown. As illustrated, the device is a“pliers type” apparatus. The device is shown clamped around the atrialtissue below the ostia of the pulmonary veins. In FIGS. 62B-62D, anelectrode needle is advanced through the atrial tissue to contact areceiver at the tip of the device. FIG. 62E shows one method of clampingthe tissue to a rigid needle electrode, using a non-rigid outer clampingmember that flexes either by further motion of the handle as shown or byfurther extension of the electrode member. FIG. 62F shows both sides ofthe clamping member flexed, and the tissue compressed between. FIG. 62Gshows the position of the clamping members and electrode prior to tissueclamping. FIG. 62H shows these positions during tissue clamping. BipolarRF energy is applied between the clamping members, and the innerelectrode to ablate the atrial tissue, creating a lesion, as shown inFIG. 62H. Note also, that if the inner electrode had only one exposedelectrode surface, the tissue ablation could be carried out first on oneside, then the other, without occluding the lumen between the pulmonaryveins and the atrium.

[0131]FIG. 62I shows another way to achieve tissue compression byadvancing a relatively flexible needle electrode which bends as shown tocompress the tissue between the electrode and one of the device jaws.

[0132] Thus, it can be seen that a transmural ablation device and methodhave been provided that overcome the limitations of the prior art.First, current technology involves ablation devices deliver ablationenergy to either the inside (endocardium) or outside (epicardium) of theheart. Using these techniques, the tissue ablation proceeds from onewall of the heart through the tissue to the opposite wall. To date,there has been no reliable way to consistently achieve lesions thatpenetrate the full thickness of the atrial wall (transmural lesions),and there has been no way to determine either continuity ortransmurality of these lesions. If the lesion does not penetrate throughenough of the atrial wall, conduction can still occur, and the lesiondoes not fully block the electrical signals that are causing thearrhythmia. Using an endocardial approach, if the lesion penetrates toofar through the wall, critical structures such as coronary arteries,veins, or the esophagus can be damaged on the outside of the heart.Using an epicardial approach, if the lesion penetrates too far, bloodcan be coagulated, or critical structures such as valves, nodes, orconnective tissue can be damaged on the inside of the heart.

[0133] There has also been no reliable and consistent way to safelyachieve fully continuous, long (greater than 1 cm) lesions in the atrialwall without a high risk of thrombus, damage to critical structures, orextensive damage to the atrial tissue.

[0134] The present invention overcomes these shortcomings because theconductive area of each electrode is very narrow compared to the widthof the clamped area. As a result, the thermal damage to the tissue isminimal. In contrast, current technology uses catheter electrodes whichare typically 1 or 2 mm diameter requiring a lesion width of almost 8 mmto achieve a depth of 5 mm. Using the present invention, a lesion depthof 5 mm with a width of less than 2 mm can be achieved. This aspect ofthe invention allows for longer linear lesions with less power deliverybecause less tissue is being heated. There is, therefore, considerablyless damage to healthy atrial tissue for a lesion of a given depth andlength. Recent efforts in creating linear lesions using endocardialelectrodes resulted in ablation of over 20% of the atrial endocardium,and a commensurate decrease in atrial contractility.

[0135] Another advantage of this device is that ablation can be done ona beating heart. Using a high modulus material such as tungsten orcarbon fiber would allow a minimum diameter, and a maximum clampingpressure for a given clamping length. Once the device is clamped ontothe atrial wall, the position of the electrodes can be verified byvisually inspecting the position of the outer electrode before deliveryof RF energy. If the clamping pressure is higher than the atrialpressure, then clamping over a coronary artery would cut off blood flow,and the resulting change in the EKG would act as a warning to the userprior to applying RF energy. The clamping will prevent any movement ofthe electrodes relative to the heart wall, and RF energy can be appliedwith confidence that the ablated tissue will be contained completelybetween the two electrodes.

[0136] Another important feature of this device is that the energytransfer is limited to the tissue clamped between the two electrodes.The insulated electrodes protect structures on the outside of the heartfrom being exposed to RF energy. Because of this limitation of currentflow, damage to critical structures can be avoided.

[0137] Another advantage of this device is that it can easily be adaptedto a minimally invasive thoracoscopic approach. The device shown hasbeen reduced to a 5 mm diameter device, and can probably be reduced to 3mm or less. Using video thoracoscopy, the device could be introducedthrough a small intracostal incision, and used to create fullytransmural linear lesions on a beating heart, possibly under localanesthesia on an anesthetized patient.

[0138] Accordingly, a device for performing transmural ablation has beenprovided that meets all the objects of the present invention. While theinvention has been described in terms of certain preferred embodiments,there is no intent to limit the invention to the same. Instead it is tobe defined by the scope of the appended claims.

What is claimed:
 1. A device for clamping and ablating cardiac tissuecomprising: a first handle member; a second handle member pivotallyconnected to the first handle member; first and second mating jawmembers associated with the first and second handle members,respectively, the jaw members each having a distal tip and being movableby the handle members between a first open position and a second clampedposition, the jaw members having insulated outer surfaces with convex,opposed mating surfaces, each mating surface having a central peak, thecentral peak of the first jaw being aligned with the central peak of thesecond jaw; a first elongated ablation electrode extending along thecentral peak of the first jaw member; a second elongated ablationelectrode extending along the central peak of the second jaw member; thefirst and second ablation electrodes being adapted to be connected to anRF energy source so that, when activated, the first and second ablationelectrodes are of opposite polarity; and one of said first and secondjaw members including a pair of EKG monitoring sensors on the tip spaceddistally from its associated ablation electrode for contacting cardiactissue and being adapted to be connected to an EKG monitor, so that whencardiac tissue is grasped between the first and second jaws, the EKGsensors contact the cardiac tissue and transmit the signals generated bythe tissue to the EKG monitor.
 2. The device of claim 1 wherein theelectrodes are between approximately 3 to 8 cm in length andapproximately 0.12 to 0.6 mm in width.
 3. The device of claim 1 whereinthe electrodes comprise gold-plated copper.
 4. The device of claim 1wherein one of the jaws is fixed and the EKG monitoring sensors areassociated with the fixed jaw.
 5. A cardiac tissue grasping apparatuscomprising: first and second grasping jaws, the grasping jaws eachhaving a distal tip and being relatively moveable between open andclosed positions; each jaw including a raised electrode and a recedingclamping surface in face-to-face relation with the electrode andclamping surface of the other jaw; the clamping surfaces of the jawscomprising an insulating material and the raised, face-to-faceelectrodes being of opposite polarity and connectible to a power sourcefor providing an electrical current between the electrodes; whereby whentissue is grasped between said clamping surfaces, the electrodes aresubstantially entirely contacted by the tissue; and one of said firstand second grasping jaws including a pair of EKG monitoring sensors onthe tip spaced distally from its associated electrode for contactingcardiac tissue and being adapted to be connected to an EKG monitor, sothat when cardiac tissue is grasped between the first and secondgrasping jaws, the EKG sensors contact the cardiac tissue and transmitthe signals generated by the tissue to the EKG monitor.
 6. The apparatusof claim 5 wherein the electrodes are between approximately 3 to 8 cm inlength and approximately 0.12 to 0.6 mm in width.
 7. The apparatus ofclaim 5 wherein the electrodes comprise gold-plated copper.
 8. Thedevice of claim 5 wherein one of the jaw members comprises a piercingtip adapted to puncture myocardial tissue.
 9. The device of claim 5wherein one of the jaws is fixed and the EKG monitoring sensors areassociated with the fixed jaw.